Shell and Tube Heat Exchangers

To be able to transfer heat effectively, the tube material should have good thermal conductivity. Heat is transferred from a hot fluid to a cold fluid through the tubes, creating a temperature difference across the wall of the tubes. Thermal stresses occur during operation due to the tendency of tubes to expand and contract with temperature fluctuations; this in addition to any stress from high fluid pressures. The tube material also should be compatible with both the shell and tube side fluids for long periods under the operating conditions (temperatures, chemical compatibility, pH, etc.) to minimize deterioration. All of these requirements call for careful selection of strong, thermally-conductive, corrosion-resistant, high quality tube materials. Typically, metals such as aluminium, copper alloy, stainless steel, carbon steel, non-ferrous copper alloy, Inconel, nickel, Hastelloy and titanium are used; fluoropolymers such as perfluoro alkoxy alkane (PFA) and fluorinated ethylene propylene (FEP) are also used as tubing materials due to their high resistance to extreme temperatures. Poor choice of tube material could result in a leak through a tube between the shell and tube sides causing fluid cross-contamination and dangerous pressure fluctuations.

Valutech works with industry leading shell-and-tube heat exchanger manufacturers to provide individually designed units to suit fluid heat transfer applications across virtually all industries. Regardless of manufacturer, there are several common design styles that are described using a standardized three-letter notation system designated by the Tubular Exchanger Manufacturers Association (TEMA). The three letters designate the front (stationary) head, the shell style, and the rear head style; the rear head style determines whether the tube bundle is fixed (welded) to the shell or if it free-floating. While fixed tube bundle constructions are more economical to build, they necessitate chemical cleaning of the outside of the tubes since they cannot be mechanically accessed, and they are not suitable for high-temperature and/or high- pressure duties where thermal expansion is a concern. The following TEMA styles are our most common offerings:

The styles in the above diagrams are known as BEM, and BEU, respectively. The ‘B’ front head refers to the bonnet style integral cover; this is the most economical style of front header in terms of capital cost, and is suitable for high pressure duties due to only having one seal. The bonnet style requires disturbance to piping in order to remove the header and access the tube bundle, and is therefore suited to clean tube-side fluids.

The style shown in the BEU diagram contains a pass partition, as illustrated by the solid light blue line. The ‘M’ style of cover is simply the rear head equivalent of the ‘B’ front head. The ‘E’ shell refers to the single- pass shell type, and is the most common style of shell for industrial applications. The ‘U’ style of rear header refers to the U-Tube construction shown above, where the tubes are floating relative to the rear header; this design has a very tight bundle-to-shell clearance, but it cannot have pure counterflow with an ‘E’ style shell, and must have an even number of tube passes. For more information on the BEU configuration and BEM configuration, please click on the respective diagram.

All our welders are ASME, AWS and API Qualified with the ability to weld carbon, low and high alloy steels, nickel and nickel alloys, copper alloys, chrome-moly, Hastelloy, Incoloy, Inconel, Duplex, and all grades of stainless steel.  Our shop has the equipment and expertise in the following welding methods:

Our craftsmen have an average of 20 years experience in the precision fabrication of custom body flanges, tube-sheets, baffles and miscellaneous components up to 30″ in diameter.  We have the ability to shear and bend plates up to ½″ thick.

Our manufacturers use high-precision automated machinery, capable of drilling deep holes to an extremely high tolerance.  Tube-sheets, baffles, and flanges are drilled using CNC equipment for accuracy and speed, and shop engineers program the equipment directly from the CAD fabrication drawings. Qualified machinists then set the piece in place and monitor the drilling process.

We have the in-house capability to bend tubes for “U-bundles”.  Our machinery and operators are skilled at bending all tube grades and sizes to a specified radius while taking into consideration reduction in tube wall thickness.

All thermal design is performed by our in-house process engineers, utilizing Aspen Tech Thermal Rating software and custom-developed programming.  We operate with the understanding that correct and thorough input is required for accurate results — our engineers use software tools to perform the design based on experience and knowledge of thermal properties. We have the capability to design all major industrial shell and tube heat exchanger equipment, including single-phase, multi-phase, condensers, evaporators, and other specialty units. We can provide complete thermal design, as well as rating or review of your calculations for value-added engineering solutions.

We continue to use the Aspen Mechanical Suite, which draws on the long heritage of the B-JAC Teams software to optimize design by recognizing the interaction of key components.  This, in conjunction with our in-house custom programmed mechanical software, provides us with the ability to minimize material usage to produce an efficient and cost-effective shell and tube heat exchanger designs.

The design and fabrication of highly complicated shell and tube heat exchangers and pressure vessels is streamlined with the use of 3D design software.  This method reduces both lead times and cost by accurately dimensioning components with challenging geometric features while verifying clearances prior to the start of fabrication.  The customer also benefits from the use of this model when creating piping plans and determining other special requirements of their plants.